Global trends and ENSO

It’s long been known that El Niño variability affects the global mean temperature anomalies. 1998 was so warm in part because of the big El Niño event over the winter of 1997-1998 which directly warmed a large part of the Pacific, and indirectly warmed (via the large increase in water vapour) an even larger region. The opposite effect was seen with the La Niña event this last winter. Since the variability associated with these events is large compared to expected global warming trends over a short number of years, the underlying trends might be more clearly seen if the El Niño events (more generally, the El Niño – Southern Oscillation (ENSO)) were taken out of the way. There is no perfect way to do this – but there are a couple of reasonable approaches.

In particular, the Thompson et al (2008) paper (discussed here), used a neat way to extract the ENSO signal from the SST data, by building a simple physical model for how the tropical Pacific anomalies affect the mean. He kindly used the same approach for the HadCRUT3v data (pictured below) and I adapted it for the GISTEMP data as well. This might not be ideal, but it’s not too bad:

(Each line has been re-adjusted so that it has a mean of zero over the period 1961-1990).

The basic picture over the long term doesn’t change. The trends over the last 30 years remain though the interannual variability is slightly reduced (as you’d expect). The magnitude of the adjustment varies between +/-0.25ºC. You can more clearly see the impacts of the volcanoes (Agung: 1963, El Chichon: 1982, Pinatubo: 1991). Over the short term though, it does make a difference. Notably, the extreme warmth in 1998 is somewhat subdued, as is last winter’s coolness. The warmest year designation (now in the absence of a strong El Niño) is more clearly seen to be 2005 (in GISTEMP) or either 2005 or 2001 (in HadCRUT3v). This last decade is still the warmest decade in the record, and the top 8 or 10 years (depending on the data source) are all in the last 10 years!

Despite our advice, people are still insisting that short term trends are meaningful, and so to keep them happy, standard linear regression trends in the ENSO-corrected annual means are all positive since 1998 (though not significantly so). These are slightly more meaningful than for the non-ENSO corrected versions, but not by much – as usual, corrections for auto-correlation would expand the error bars further.

The differences in the two products (HadCRUT3v and GISTEMP) are mostly a function of coverage and extrapolation procedures where there is an absence of data. Since one of those areas with no station coverage is the Arctic Ocean, (which as you know has been warming up somewhat), that puts in a growing difference between the products. HadCRUT3v does not extrapolate past the coast, while GISTEMP extrapolates from the circum-Arctic stations – the former implies that the Arctic is warming at the same rate as the rest of the globe, while the latter assumes that the Arctic is warming as fast as the highest measured latitudes. Both assumptions might be wrong of course, but a good test will be from the Arctic Buoy data once they have been processed up to the present and a specific Arctic Ocean product is made. There are some seasonal issues as well (spring Arctic trends are much stronger the summer trends since it is very hard to go significantly above 0ºC while there is any ice left).

Update: A similar analysis (with similar conclusions) was published by Fawcett (2008) (p141).

The ENSO-corrected data can be downloaded here. Note that because the correction is not necessarily zero for the respective baselines, each each time series needs to be independently normalised to get a common baseline.

that is not the case, it is not ignored, but because of a lack of data, we do not kow, how these events worked out in different parts of the world. What is understood though is the basic physics and we know that in increase in Greenhouse gases drives temperatures up. This is what you call a fact. The Russian chap does not deny this fact (like many sceptics do) but he states that decreased radiation from the sun will ultimatly be a stronger factor. Okay, great, now it’s up to him to prove it and his theory mus be analysed with the same rigorous scrutiny, which ist applied to the AGW theory. At Pulkovo, they sould have the resources to develop a model to Open Source it and then be open for a reality check.

Can someone run a fourier transform on the solar cycle data starting from 1610 until now? Maybe there would be a hint of ~30 year PDO/AMO cycle embedded in the results. Perhaps PDO/AMO is like an amplitude modulated signal riding on the 11 year solar cycle carier signal.

Okay. I am almost ready to concede that solar influence is less than I naivly thought. I am new to this stuff and thought that I had all the answers. I like being a contrarian. But there seems to be a change in tone from AGW proponents. Articles I have seen in the media a few years ago proclaimed that over the past 30 years Co2 from fossil fuel use has totally swamped natural variability. I think the standard AGW claim is that CO2 influence is a factor of 10 greater than that of natural variability. Now since the strong la nina AGW proponents are saying that natural variability can mask AGW. I had not heard that a la nina could dampen global temperatures until after the fact. At least that is what I have picked up on from following media stories on the subject.

Peterk.
The sun may prove the russian wrong or right in the near future. This current long solar minimum was unexpected. Dr. David Hathaway of NASA, one of the foremost authoriities on solar cycles was predicting a strong cycle 24 that should of started two years ago. Now the solar scientists who had predicted a weak cycle 24 seem to have the stronger position. There may be no need to wait decades to completely trash the russians ideas. Solar influence on climate is seriously being put to the test right now. Solar activity is low. At its current rate solar cycle 24 wont reach peak for 3 or 4 years. It is quite exciting actually. In the next 5 years if there is not a downward trend in temps then the russian should be banished to siberia. A good web site to check solar activity is : solarcycle24.com. It is run by a HAM radio operator. The HAMMIES are besides themselves with frustration. They need strong solar activity in order top have better propagation of their signals.

My category is the “we’ll go broke before we burn all the carbon fuels needed to boil the oceans” one, and I’m fairly confident that I’m more correct than the IPCC business-as-usual forecasts, and I’d argue that the current economic upheaval over oil prices bears that out. My particular form of denialism isn’t dangerous because it advocates a massive shift to renewable energy forms to avert an economic disaster which will also avert an environmental one. Based on that, I’m a relatively harmless crackpot.

But the folks who are going to latch on to the Gore Minimum and use it to “prove” that CO2 is not a problem are the ones that have to be reached, and remarks like

This was discussed over and over. We are talking about long term trends. His conclusion that one year (2007) falsifies the AGW theory is – let’s call it a bit strange. And there is no clear evidence presented for his assumed “two-century” cycle.

fly in the face of what I understand to be well-established science. What are you going to say when the sun stays spot free for a while longer and the well-established relationship between a spot-free sun and lower global temperatures begins to contradict your remarks? When year after year, there are no new global high records, what do you say?

It is interesting to watch supporters of AGW defend their position. Science is real, climate is real. How is it real (relating to the article) to take away what is happening to show what one believes should be happening? A simple proposed hypothesis: “as global atmospheric CO2 levels rise, so will global atmospheric temperature”, is not happening. Why? Because the observed “real climate” does not agree with that proposed hypothesis.

In “real science”, this is a primary reason to question the proposed hypothesis.

I would also note that if we accept the definition of climate as “mean regional or global weather over a period of 30 years or more”, then shouldn’t we be using the 30 year period 1978 through 2008? Would not, then, the last 10 years be a full third of the entire period? Why is the time between 1998 to 2008 considered too short a period to be valid? I believe the answer is clear: the last 10 years do not fit the proposed hypothesis, therefore they must be rationalized away in some manner.

If the AGW by CO2 emission proposed hypothesis is correct, the raw data and observation should show it clearly. Not predictive models, not “what if” scenarios, not manipulated figures – raw data and observation.

So far, they do not.

[Response: Your point illustrates very clearly why ‘armchair science’ has more in common with armchairs than science. First off, your supposition that increasing CO2 leads to more warming is fine as a general principle but in any actual application you have to caveat it with ‘all else being equal’ and an appreciation of the signal to noise ratio in any finite time series. That means that if something else is going on – a big volcano for instance – you need to consider those changes too. But the biggest issue is one of signal vs noise. There is more CO2 in the air today than this time last year – yet do you expect that extra 2ppm to translate to a measurable 0.02 deg C change in the global mean temperature? No. The standard deviation from one year to another in these records is between 0.1 and 0.2 deg C – therefore the year to year variation will swamp the expected change. After 30 years, the single will be clear (as indeed it is) since the expected change (~0.5 deg C) is larger than the variability. If you take shorter periods the signal to noise ratio goes down – how is this controversial? We build models to quantify these expectations more precisely and for the recent period, the models show a range of behaviours (while all showing a long term trend) which easily span the observed behaviour. In order to falsify a proposition you need to show that the result is in fact outside of the expected range of behaviour. Does the fact that is cooler today than yesterday imply that summer is now over? – gavin]

Steve Reynolds, The question is not whether a low climate sensitivity is consistent with any one particular set of data, but which sensitivity is most consistent with all the data. This is a much more powerful constraint. The thing is when you look at only one dataset, yes, you see that low values of sensitivity may be possible–but you also can’t eliminate 6 degrees per doubling, and that would be catastrophic. Personally, I would be much more satisfied if we could reduce the probability that sensitivity is >4.5 degrees per doubling than if we could raise the probability that it’s less than 2 degrees per doubling. That makes the problem much more manageable from the point of view of risk management.

Now since the strong la nina AGW proponents are saying that natural variability can mask AGW. I had not heard that a la nina could dampen global temperatures until after the fact. At least that is what I have picked up on from following media stories on the subject.

If you look at all the published charts, it’s obvious that there are natural variations that can overwhelm the upward trend due to CO2.

What you see in the media is a focus on a small number of components of the larger situation. Yes, there are natural variations, and yes, sometimes the natural variation overwhelms something else, such as the changes caused by rising CO2 levels.

So the “natural variations” folks emphasize “natural variations” and ignore “rising CO2 levels”, while the other side does the opposite. Or put another way, the proof of the “hockey stick” isn’t the part that hits the puck, it’s the handle. If, as folks like myself argue, the puck-hitting-part is dominated by strong solar cycles 22 and 23, you still have to deal with the rise in global temperatures from before that. And if cycles 24 and possibly 25 are below normal, someone has to explain “natural variability” so that declines in either absolute temperature or rate of increase don’t serve to discredit the overall “increases in CO2 level cause increases in global temperature”.

The giant ball has some behavior and its over 8 billion years old so its hard to understand what its behavior over time is. We know with more surety the 11.1 year cycle, beyond that it turns more into a fuzzy ball. Of course there is the luminosity increase but that is truly minuscule in forcing amount on small time scales such as the warming recently understood in the earth climate (since the beginning of the industrial age).

What is the Gore Minimum? Do you have relevant data on this? Never heard of it before. Okay, I just googled it. It looks like some people want to call the next solar activity minimum the Gore minimum or the Hansen minimum as a way to ridicule them. Let’s try to stick to the facts of the science and what can be understood from that.

Just for fun, let’s postulate what would happen to our warming trend if the sunspot activity died. Please for give my gross oversimplification.

If we have no sunspot activity we lose .3 W/m2 of forcing.

The current forcing is calculated around 1.9 W/m2

1.9 – .3 = 1.6 W/m2

Well, looks like we will still warm. As mentioned previously, there is a lot of extra forcing in the system and it will take time for the ocean to absorb the energy and give us a new equilibrium to forcing ration/balance.

Why don’t we call the next extended solar minimum the ‘I wish it were cooler minimum’. That might be more appropriate.

PeterK,
Did Creighton produce this graph. Just eyeballing it looks like B (the “likely” one) is off by .25 to .3, about half the trend from 1880-1988.

[Response: Brought to you by the magic of natural variability… – gavin]

So if someone were to say,

“Just to make things clear: we are not stating that anthropogenic climate change won’t be as bad as previously thought”…“What we are saying is that on top of the warming trend there is a long-periodic oscillation that will probably lead to a to a lower temperature increase than we would expect from the current trend during the next years”

Would that be considered reasonable? Or is that the kind of statement which,

… could backfire against the whole climate science community if the forecast turns out to be wrong.

I note Gavin, that you did not sign onto this, and precisely because you did not add your name, I would value your viewpoint.

Gavin: The ENSO Corrected data set you provided has an outlier in the “GISTEMP (ENSO Corrected)” data at 1928.88. The value reads 7.229e-0. Please advise if that should end with -01 or -02, as opposed to -0.

That step change is normally evident in any comparison of HADSST or HadCRUT data with another data set: GISTEMP, NCDC, or the two satellite versions, and, obviously, ERSST.v2 and ERSST.v3. It is visible in the longer-term graph above, but disappears in the short-term illustration. How’d you make it disappear? Just curious.

I doubt any good climatologist would ignore natural variability but you have to recognize context and keep it in your head. Then put what you hear in context of that. Natural variability will not go away, but certain forcing components will drive us in another direction.

Think of it this way (I am not advocating drinking and driving) Let’s say you drink to much and start driving toward home. Your car is wavering due to the slow response time caused by increased alcohol in your bloodstream impairing judgment. You correct and get back toward the lane but you over correct, which leads to another correction to try to stay on the road. In this example, you are on the road and heading in the direction you should be, but the car is weaving a bit. That is you staying within natural variability (you have not hit a tree, or another car yet) in the expected direction based on the fact you are on the right road.

Now let’s look at AGW and drunk driving. Let’s say you are fairly well impaired? And you accidentally get on the wrong road? Now you are going in a new direction. But you are still doing the same wavering you were doing before. Just on a different road.

In other words, you changed course and are no longer going where you expected at the start of the trip i.e. destination home… now you are going somewhere else but you are still wavering on the path (natural variability, warming and cooling short term trends in the new long term trend).

Natural variability wont go away, it will just be doing its thing on a new road.

A statistician who goes by the name of Tamino has done the Fourier analysis in exquisite detail here. Not a hint of any kind of periodicity in the temperature record, let alone anything that correlates with sun activity.

I wouldn’t rely too much store on what media articles tell you about the science. The dodginess of media reporting is a regular topic of conversation here at RealClimate and at many other sites devoted to climate science.

In #53 iceman wrote “But there seems to be a change in tone from AGW proponents. Articles I have seen in the media….”

The key phrase, iceman, is “in the media.” The popular media very often are just plain wrong. Even scientifically literate popular media often overstate the scientists’ claims, in order to make succinct, catchy headlines, in order to attract readers. And scientists themselves often make statements to the media, that are incorrect when interpreted without the context that is in the scientists’ heads and in the scientific literature.

One piece of advice. Don’t listen to the media and expect to get science. Their job is controversy, because controversy sells. Another reason not to listen to the media is the Monsanto/Fox news case which made it to the supreme court in Florida. They basically said it is not illegal for the news to lie. So if they do they can’t be prosecuted. Isn’t that lovely.

None of this speculation is new, and all of it has been addressed. Yes, climate scientists looked at the rising temperatures since 1880, the cooling around 1940 and the subsequent warming and attempted to correlate those patterns with solar patterns. No, that doesn’t work to explain the current warming.

Please if you’re going to speculate about solar activity affecting the earth’s climate, address the existing scientific record so that we know that you’ve done your homework. Most of you are just posting nothing more than “have you ever thought about the sun, huh, have you?”. Yes, its been done.

First, I (and many others) have been all over the sunspot data and there’s no hint of a cycle near 30 years. Second, the figure 30 years for the PDO/AMO is *not* a cycle — it’s a “characteristic time scale.” There’s no evidence that PDO and AMO are periodic, or even nearly so.

Probably much of your confusion originates from misinformation you’ve received. For example, you say “I think the standard AGW claim is that CO2 influence is a factor of 10 greater than that of natural variability.” Where did you get this, and precisely what does it mean?

> Thompson et al (2008) paper (discussed here), used a neat way to extract the ENSO
> signal from the SST data, by building a simple physical model for how the tropical
> Pacific anomalies affect the mean. He kindly used the same approach for the
> HadCRUT3v data … and I [Gavin] adapted it for the GISTEMP data as well.

Writing as I always do from the peanut gallery, a Thank You to Dr. Thompson — and I’m curious what more the researchers have to say about the method and where else it may be useful. Is it possible to generalize and describe this as a statistical tool?

Cite them so you can tell others exactly what you’re talking about and people can read them for themselves instead of trust your recollection.
Look at the writer’s record. Look at the sources the writer gives (if any). Look at the papers, the footnotes, and then click the ‘cited by’ and the ‘similar’ links available online for most contemporary science paper abstracts.

You can take one PR press release reported by a handful of media sources and commented on fifty times by five regular blogfloggers, and think something’s happened.

I’m a beginner too (my first serious look at the RealClimate site). On a similar topic, for fun, I did the FFT for global temperature (several incarnations) and sunspots (one incarnation) On that limited basis, there seemed to be a connection between global temperature and sunspot numbers.

Seeing a connection, I created a fairly straight forward model of global temperature vs sunspots, etcetera. It incorporated limited unsubstantiated assumptions (based on general physics and my reading of the blogosphere literature) regarding mechanisms. It did not include CO2 effects (as I wanted to see if sun alone could explain things, to a first order). The model “fit” the HadCrut2 data quite well from 1880 to present (with about 0.2C left to explain during the last 10 years). The fit to HadCrut3 was not as good from 1860 to present (leaving 0.3C). Looking at areas of misfit, volcanoes, El Nino, etc seemed to be affecting those areas.

Interesting, but no more than that (if I did it, it can’t be new news).

I remain open minded regarding the relative importance of sun and anthropogenic mechanisms to global temperatures over the next 100 years.

I think I am going stop posting and just read. To quote “The Rock”, “Know your role and shut your mouth”.
My role is learn more and not waste peoples time til I find out more about the subject. Really glad I stumbled onto this site.

Hmmm. I see my #71 findings contradict #64 (which was written as I posted) — no harm intended. Bottom line, in a topic as controversial as this one, I am slow to submit to authority (on either side) :) Rather, I like to try these things for myself when I can.

The ripple effect
The state’s water crisis is taking a withering toll on life on the Valley’s west side.
By Dennis Pollock and Robert Rodriguez / The Fresno Bee
07/05/08 21:48:39

Life on the Valley’s west side may be withering along with crops that farmers have left to die.

Hundreds of farmworkers already have lost their jobs as growers idled or abandoned crops because of severe water shortages. Hundreds more will lose work because of crops that won’t be planted this autumn.

Signs of trouble are everywhere:

The Spreckels Sugar plant in Mendota, a fixture since 1963, will close in September unless a grower cooperative can salvage it. Closure would mean 200 jobs lost.

Fordel, a major grower-packer-shipper of melons and other produce, is selling its Mendota facility after more than two decades. It is not harvesting or packing a crop this year. City officials say the company accounted for as many as 500 growing and packing jobs.

St. Joseph’s School in Firebaugh is closing this month after more than 40 years, a casualty of declining enrollment and a shrinking pool of farmers able to give money.

Weather and pest challenges, along with abandoned acreage, are cutting processing-tomato production for Fresno County, the state’s top grower, by as much as 400,000 tons. In 2006, the last year for which figures are available, farmers in Fresno County produced 4.4 million tons of processing tomatoes valued at $248 million. This year’s cut will mean shorter hours of plant operation and less work for truckers.

Thousands of acres of cotton are being abandoned at a time when planted upland cotton acreage already was at its lowest level on record. In addition, windy weather and roller-coaster temperatures have taken their toll.

Gavin mentioned and linked to the Arctic Buoy program in the original post. The linked article from 2000 led me to the home pagehttp://iabp.apl.washington.edu/index.html
Their 2008 annual meeting (late June) draft agenda includes:

I don’t like bets. Would one bet on the view of one Russian institute that solar activity will decrease. As many readers pointed out, the sun is a huge gasball in the solar system and we do not know too much about its behaviour. The logical conclusion is to continue with our current beahviour and place a bet that a decrease in sun radiation will compensate for this (Irony). Brilliant idea. We do not understand our planet but we will instead predict the behaviour of a star. That’s like a stone age man who refuses to learn to light a fire and starts directly with the construction of a nuclear reactor. Good luck to him.

Ray: The thing is when you look at only one dataset, yes, you see that low values of sensitivity may be possible–but you also can’t eliminate 6 degrees per doubling, and that would be catastrophic.

Annan (2008) seems to do a pretty good job of eliminating sensitivity >3.6C with one data set (and a reasonable prior), although more data sets would add to the confidence.

Ray: Personally, I would be much more satisfied if we could reduce the probability that sensitivity is >4.5 degrees per doubling than if we could raise the probability that it’s less than 2 degrees per doubling.

Yes, but even better to show 1.5C the most likely sensitivity and 3C the maximum.

Given the nature of the subject studied — the practice of posting across various forums lies thinly disguised as “questions” — my characterization would rather be “forensic sleuth”. Or perhaps “natural forensic sleuth”… Hank is a natural. Every teacher knows this technique for catching student plagiarism :-)

I know what HAM is, I run a self compiled Linux system. Yes, the debate about solar cycles is interesting and tamino performed a great job. Thanks 64 for the link and tamino for his comment.

Maybe, I can unterstand you better, because I am a former sceptic and it needs a lot of reading and the willingness to accept that there are open questions. It was only this Blog, not the mainstream media, which finally convinced me. It is not helpful to talk about denialists because it is important for the scientific process that people stand up, get involved and raise valid questions, that’s what we call a democracy.

@tamino

What do you think about the Russian stuff and his ideas about solar cycles (e.g. 200 years)? I mean, this guy is not an idiot, even, if I have problems to find a relevant link to climate science, it does not mean that everything from this guy is pure crap.

Major thanks go to Gavin and the RC-team, this is by far one of the best blogs.

Steve Reynolds, Actually, moving the most likely value from 3 down to 1.5, while still leaving substantial probability for levels above 4.5 really doesn’t help us all that much in terms of risk mitigation–that’s been my point all through such discussions. First, if we reach a point where natural ghg emissions (from oceans, permafrost, etc.) ever swamped anthropogenic emissions, then we’re screwed regardless of sensitivity.
Second, looking at it in terms of risk, the consequences of high sensitivity are so catastrophic that they dominate risk even for pretty modest probabilities. James Annan’s Bayesian approach is not unreasonable, but the choice of location for the Prior is highly subjective–and not at all conservative. It may give us a warm fuzzy, but I wouldn’t drive a car over a bridge that used similar techniques.
Finally, many of the same changes that must occur due to climate change must also occur as a result of Peak Oil. Certianly, limitations of energy supply will require decreased consumption in the near term. We will have to come up with different energy solutions. The main difference is that climate concerns force us to leave carbon where it is–sequestered in the ground as coal, tar sands, oil shale, etc., in the Oceans as clathrates and so on.

At this point, arguments for doing nothing are very difficult to justify.

Steve Reynolds (28) — Naturally one has to consider as much data as possible and even then one still cannot rule out very low or very high climate sensitivites entirely by these probablistic techniques. Another method is to look at the climate sensitvites of the various GCMs; for this see IPCC AR4 WG1 report. So far, using as much as one can find, climate sensitivity of 3 +- 0.2 K seems the best estimate. Wider error bars cannot be excluded, of course.

iceman & PeterK — I used a periodogram technique for finding quasi-periodic signals in the temperature anomalies of the GISP2 ice core temperature proxies by Alley, but just for the Holocene. There is nothing detectable by this method for intervals from 22 to 45 years and again from 90 to 300 years. Between 45 and 90 years there seems to be something which could be attributed to the various ocean oscillations. It would, I think, take a wavelet technique to tease out if there is actually anything there; I’m not up on how to do that, so I’ll take a pass on doing anything further with this.

However, in his article on his website Abdusamatov makes such a claim. I do not know, if the magazine is good enough and if would be seen as peer reviewed. Generally (and I am a former sceptic) this guy causes us a lot of trouble. In our forum in Germany we now have close to 9.000 postings, so really any comment or any article from Gavin, Raypierre or Stefan on Pulkovo would help. I am still open minded don’t get me wrong, if the Rusian guy would be correct, no problem, but I doubt it.

My apologies to all. I think my fingers are superseding my brain today. Another correction to my own posting.

There has thus far been no model or even substantive reasoning that can explain this recent warming.

should include

; other than the current GCM’s that include known quantities of industrial based GHG’s and forcings.

#75 iceman

“Welcome, to the ‘real’ world.” as Morpheus would say. The science is the science, there are plenty of questions to be answered, but what we do know with confidence is strong enough to base policy decisions on. Unfortunately that means individuals need to understand the science. Because individuals drive politicians, they don’t lead much theses days, they pretty much follow. I would not wait for them to figure it out on their own.

“The potential for self-delusion is significantly enhanced by the fact that climate data generally does have a lot of signal in the decadal band (say between 9 and 15 years). This variability relates to the incidence of volcanic eruptions, ENSO cycles, the Pacific Decadal Oscillation (PDO) etc. as well as potentially the solar cycle. So another neat trick to convince yourself that you found a solar-climate link is to use a very narrow band pass filter centered around 11 years, to match the rough periodicity of the sun spot cycle, and then show that your 11 year cycle in the data matches the sun spot cycle. Often these correlations mysteriously change phase with time, which is usually described as evidence of the non-linearity of the climate system, but in fact is the expected behaviour when there is no actual coherence. Even if the phase relationship is stable, the amount of variance explained in the original record is usually extremely small.”

Ray: James Annan’s Bayesian approach is not unreasonable, but the choice of location for the Prior is highly subjective–and not at all conservative.

I think Annan would disagree about it not being conservative. Do any real experts have an opinion on this?

Ray: Finally, many of the same changes that must occur due to climate change must also occur as a result of Peak Oil. Certianly, limitations of energy supply will require decreased consumption in the near term.

That seems doubtful to me. Price increases will limit oil consumption growth, but the Chinese and Indians seem likely to continue their energy growth with pretty much unlimited coal.

Longer term solutions involving nuclear and efficient renewables seem more practical to me than trying to convince people to accept a low standard of living.

A couple of words about our star. Upcomment, someone misstated its age as 8By, the correct figure is pretty close to 4.6By (probably a bit lower, as the age of the earth is now pinned down to 4.57By). If the sun were 8By old, the oceans would have already boiled and our planet would be devoid of life.

Another statement was made to the effect that we don’t understand the earth, how could we hope to understand the sun. The implications is that the physics of the sun (or of the solar magnetic cycle), are very much tougher than of the earth. I would think just the opposite is true. The solar cycle can be is a result of a convecting plasma in a differentially rotated star. The only difficulty is in working out the relevant MHD equations. Admittedly this is a difficult problem, and it hasn’t and won’t receive the same level of resources as the earths climate system, precisely because the odds of it having a large effect on the earth are deemed a lot smaller than the combination of natural variability and anthropgenic effects on the climate. In any case the relative difficulty of different problems in science cannot be so causally determined.

Steve Reynolds (90 & 91) — The Annan/Hargreave Bayesian priors can be done in an ‘objective’ manner by using maximum entropy methods to determine the prior distribution. One is allowed to use all known physics excluding only the observations which are going to inform the posterior distribution. To be sure that information is not used twice, once in forming the prior and once in forming the posterior, a conservative approach is to use only that physics which was known before the observations were taken.

In the simplest case, the normal distribution is appropriate; use a corrected Arrhenius approach to determine a mean and variance for the climate sensitivity. (Some may object that this gives nonzero probabilities to negative climate sensitivities.)

The evidence is that the GCMs, being based on physics, model climate and paleoclimate rather well. I have no idea what else you require?

I’ve seen ‘most likely estimates’ ranging from 2.8 to 3.2 K; around 3 K. I’m not claiming tight error bars for this. Anyway, not just yet.

Steve, the whole point of the GCMs is that they are based on physics, and if the models work better with a value of 3, that is evidence of a sort as long as the physics is not wildly off. We think the physics is right, but if it is wrong, it’s as likely to be wrong in the direction that makes things worse as that which decreases concern. The error bars are probably a standard deviation of the model results, right Dave?

Steve, Coal is not as versatile as petroleum–so changes in infrastructure will be needed globally. It is a question of whether we take the opportunity to push them away from fossil fuels or whether we replace one addiction with another.

“Another statement was made to the effect that we don’t understand the earth, how could we hope to understand the sun. The implications is that the physics of the sun (or of the solar magnetic cycle), are very much tougher than of the earth. I would think just the opposite is true. The solar cycle can be is a result of a convecting plasma in a differentially rotated star. The only difficulty is in working out the relevant MHD equations. Admittedly this is a difficult problem, and it hasn’t and won’t receive the same level of resources as the earths climate system, precisely because the odds of it having a large effect on the earth are deemed a lot smaller than the combination of natural variability and anthropgenic effects on the climate. In any case the relative difficulty of different problems in science cannot be so causally determined.”

Having actually taken an undergraduate level course in stellar models and interiors, it is a little more complicated than that, but generally you are correct that its easier to understand the sun than it is to understand a global climate model for the Earth. With the sun we can also observe that other ~1.0 solar mass stars tend to not be highly variable, and it is a relatively easy problem (compared to other global climate measurements) to measure the suns output which is the important input quantity. Coming from at least an undergraduate background in astrophysics, I’m not at all surprised that the Sun is not the most important factor in global climate variability.

Everyone trying to look for patterns in solar variability and climate change should also probably broaden their horizons and look at the Milankovich cycles and the Ice ages. Over the past million years we can probably set upper limits on how much intrinsic variability there could have been in the solar output by looking at the magnitude of the variability of the solar forcing due to the orbital changes in the earth and how those caused the Ice Ages. If you perturb the intrinsic solar output too much you would destroy that relationship and in the extreme you would not have a stable, cold Earth and would melt the poles if you included too much variability.

Iceman, don’t worry, you are not the only lay person here! I’m no scientist either, but from what I (think that I) understand of the scientific arguments, the AGW thesis is, unfortunately for all of us unless we do something quickly, strongly supported. But RealClimate is always a great place to visit for a read: informative and somethimes also provocative articles, great range of responses, interesting pesonalities in the discussion and debate, very useful references, and even the insults are reasonably polite and often funny.

Gavin, maybe you can explain how you adapted the procedures that Thompson et al used to correct HadCRUT3v, to correct GISTEMP instead. So far it seems to me that Thomson et al proved that, without the El Niños in 2002, 2005 and 2007, there has been cooling since 2000. I have serious doubts that the methods they used to extract the ENSO signal are valid, but I have even more doubts about yours because you didn’t even describe them. You just say “I did the same and look”. I am not sure that you corrected the Arctic data, which is included in GISTEMP but not in HadCREUT3v, for example. If you didn’t, then you didn’t follow the same procedures.

[Response: The method is described in the Thompson et al paper (see the “methods” section). I just applied the same delta’s from Thompson’s analysis of HadCRUT3v (which is not what used in the paper) to GISTEMP – nothing fancy. But if you want to see what other methods would show, read the Fawcett paper linked above. – gavin]